全文获取类型
收费全文 | 1048篇 |
免费 | 2篇 |
国内免费 | 104篇 |
专业分类
航空 | 401篇 |
航天技术 | 146篇 |
综合类 | 232篇 |
航天 | 375篇 |
出版年
2022年 | 2篇 |
2021年 | 7篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 26篇 |
2017年 | 16篇 |
2016年 | 21篇 |
2015年 | 14篇 |
2014年 | 19篇 |
2013年 | 70篇 |
2012年 | 89篇 |
2011年 | 99篇 |
2010年 | 32篇 |
2009年 | 51篇 |
2008年 | 42篇 |
2007年 | 28篇 |
2006年 | 10篇 |
2005年 | 20篇 |
2004年 | 94篇 |
2003年 | 80篇 |
2002年 | 119篇 |
2001年 | 137篇 |
2000年 | 61篇 |
1999年 | 3篇 |
1998年 | 17篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 9篇 |
1991年 | 18篇 |
1990年 | 6篇 |
1989年 | 32篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1981年 | 4篇 |
排序方式: 共有1154条查询结果,搜索用时 31 毫秒
971.
C. Feiler M. Buser E. Kajari W. P. Schleich E. M. Rasel R. F. O’Connell 《Space Science Reviews》2009,148(1-4):123-147
In the present paper we follow three major themes: (i) concepts of rotation in general relativity, (ii) effects induced by these generalized rotations, and (iii) their measurement using interferometry. Our journey takes us from the Foucault pendulum via the Sagnac interferometer to manifestations of gravito-magnetism in double binary pulsars and in Gödel’s Universe. Throughout our article we emphasize the emerging role of matter wave interferometry based on cold atoms or Bose–Einstein condensates leading to superior inertial sensors. In particular, we advertise recent activities directed towards the operation of a coherent matter wave interferometer in an extended free fall. 相似文献
972.
S. Kobayashi N. Hasebe E. Shibamura O. Okudaira M. Kobayashi N. Yamashita Y. Karouji M. Hareyama K. Hayatsu C. d’Uston S. Maurice O. Gasnault O. Forni B. Diez R. C. Reedy K. J. Kim 《Space Science Reviews》2010,154(1-4):193-218
The Kaguya gamma-ray spectrometer (KGRS) has great potential to precisely determine the absolute abundances of natural radioactive elements K, Th and U on the lunar surface because of its excellent spectroscopic performance. In order to achieve the best performance of the KGRS, it is important to know the spatial response function (SRF) that describes the directional sensitivity of the KGRS. The SRF is derived by a series of Monte Carlo simulations of gamma-ray transport in the sensor of the KGRS using the full-fledged simulation model of the KGRS, and is studied in detail. In this paper, the method for deriving absolute abundance of natural radioactive elements based on the SRF is described for the analysis of KGRS data, which is also applicable to any gamma-ray remote sensings. In the preliminary analysis of KGRS data, we determined the absolute abundances of K and Th on the lunar surface without using any previous knowledge of chemical information gained from Apollo samples, lunar meteorites and/or previous lunar remote sensings. The results are compared with the previous measurements and the difference and the correspondence are discussed. Future detailed analysis of KGRS data will provide new and more precise maps of K, Th and U on the lunar surface. 相似文献
973.
用惠普RGS实现CAE仿真远程操作 总被引:2,自引:0,他引:2
惠普公司的创新性软件RGS是一款操作简便、实时性强、图像丢失率极少的远程交互式软件. 相似文献
974.
放眼全世界,越来越多加工制造业的公司想要踏进航空航天市场的门槛,订单的竞争是非常激烈的.除了设计、材料、加工方案、品质、灵活性和可靠的交货时间,航空公司还期望供应商能提供他们最低的单件报价.
英周航空零件制造商NORCOT机械集团的产品经理史蒂夫·福格同样感受到了竞争带来的压力:"过硬的加工能力和丰富的经验在我们这个行业通常是立足之本,但是,我们的客户在零部件采购方面正变得越来越全球化. 相似文献
975.
In this paper, we present the results of the experimental studies of the average heat transfer value in a hemispherical recess
placed in the first, third, and fifth rows of the recess array when varying the frequency of the imposed air velocity fluctuations
in the channel. The range of the Reynolds and Strouhal number variations corresponded to operating conditions of the turbine
blade cooling systems. 相似文献
976.
The results of studying the average and local heat transfer on the surface of hemispherical protrusions arranged on one side
of the flat channel are presented. The experiments were carried out at the turbulent flow regime in varying the density of
protrusions arrangement and the channel height. 相似文献
977.
978.
M. V. Klimenko V. V. Klimenko Yu. N. Koren’kov F. S. Bessarab I. V. Karpov K. G. Ratovsky M. A. Chernigovskaya 《Cosmic Research》2013,51(1):54-63
A study of the response of the thermosphere and ionosphere to sudden stratospheric warmings (SSWs) which occurred in January of 2008 and 2009 is presented. The Global Self-consistent Model of the Thermosphere, Ionosphere, and Protonosphere (GSM TIP) developed in the West Department of IZMIRAN was a theoretical basis for this study. A comparison of the simulation results of the thermosphere-ionosphere response to SSW events with the observational data over Irkutsk and also with theoretical and experimental studies carried out during the recent years is performed. SSW events were modeled by setting disturbances in the neutral temperature and density at the lower boundary of the GSM TIP model (80 km above the Earth’s surface). It is shown that the disturbances related to SSW lead to substantial global effects in the thermosphere and ionosphere. The analysis of the experimental data showed that, in spite of very similar solar and geophysical conditions on the background of which two considered stratospheric warming events happened, the occurring disturbances in temperature at heights of the mesosphere and lower thermosphere differ substantially from each other, although some common regularities still take place especially at heights of the ionospheric F region. 相似文献
979.
较详细地研究了涵道尾桨的涵道与内桨的拉力分配关系。文中引入一拉力分配因子q,表示涵道尾桨的涵道拉力与总拉力之比。从动量原理出发,推导出静止(悬停)和轴流(直升机侧风)状态下的涵道尾桨拉力、需用功率与气流速度的关系式,分三种情况对比分析了涵道尾桨与孤立尾桨的拉力、功率和桨盘面积,得出了一些结论。结果表明,虽然在静止状态涵道尾桨的涵道提供的拉力可达总拉力的50%,但对于轴流状态、涵道尾桨的涵道的拉力增益迅速下降,取决于气流速度比。 相似文献
980.
CHAOTIC MOTION OF AN ELASTIC CIRCULAR PLATE 总被引:1,自引:0,他引:1
研究了一轴对称弹性圆板的混沌运动。计入板的几何非线性—大挠度效应,利用虚位移原理,导出了板的非线性动力方程。采用Melnikov函数、Poincare映射、相平面轨迹等工具,判断板是否发生混沌运动。 相似文献